Chapter 7, Problem 7.56P

Refrigerant 134a enters an air conditioner compressor at 4 bar, 20°C, and is compressed at steady state to 12 bar, 80°C. The volumetric flow rate of the refrigerant entering is 4.5 m³/min. The work input to the compressor is 72 kJ per kg of refrigerant flowing. Neglecting kinetic and potential energy effects, determine the magnitude of the heat transfer rate from the compressor, in kW. Q cv = 36.607 x KW

Refrigerant 134a enters an air conditioner compressor at 4 bar, 20°C, and is compressed at steady state to 12 bar, 80°C. The volumetric flow rate of the refrigerant entering is 7 m3/min. The work input to the compressor is 105 kJ per kg of refrigerant flowing.Neglecting kinetic and potential energy effects, determine the magnitude of the heat transfer rate from the compressor, in kW.

Steam enters the first-stage turbine at 40 bar and 500 °C with a mass flow rate of 17.36 k9. Steam exits the turbine at 20 bar and 400 °C. The steam is then reheated at constant pressure to 500 °C before entering the second-stage turbine. Steam leaves the second-stage turbine at 0.6 bar. For operation at steady state, and ignoring stray heat transfer and kinetic and potential energy effects, sketch a T – s diagram of processes 1-4 and determine: (a) The entropy generated in the first-stage turbine [0.64 kW/K] (b) The isentropic efficiency of the first-stage turbine [89%] (c) The exit temperature of the turbine 2 if its isentropic efficiency is nT, = 0.85 [130 °C] (d) The entropy production in the reheater if the average boundary temperature is 600 °C [0.91 kW /K] Steam + P = 40 bar T = 500°C (AV), = 90 m³/min P4= 0.6 bar Power Turbine Turbine P2 = 20 bar T = 400°C Reheater P = 20 bar T3 = 500°C 2 Qreheater

Carbon dioxide gas is compressed at steady state from a pressure of 22 lbf/in2 and a temperature of 32oF to a pressure of 50 lbf/in2 and a temperature of 110oF. The gas enters the compressor with a velocity of 30 ft/s and exits with a velocity of 80 ft/s. The mass flow rate is 4000 lb/hr. The magnitude of the heat transfer rate from the compressor to its surroundings is 5% of the compressor power input. Use the ideal gas model with cp = 0.21 Btu/lb·oR and neglect potential energy effects.

Air enters a compressor operating at steady state at 14.7 lbf/in.2 and 60°F and is compressed to a pressure of 150 lbf/in.2 As the air passes through the compressor, it is cooled at a rate of 10 Btu per lb of air flowing by water circulated through the compressor casing. The volumetric flow rate of the air at the inlet is 5000 ft3/min, and the power input to the compressor is 700 hp. The air behaves as an ideal gas, there is no stray heat transfer, and kinetic and potential effects are negligible. Determine (a) the mass flow rate of the air, lb/s, and (b) the temperature of the air at the compressor exit, in °F.

Steam enters a one-inlet, two-exit control volume at location (1) at 360°C, 100 bar, with a mass flow rate of 2 kg/s. The inlet pipe is round with a diameter of 5.2 cm. Fifteen percent of the flow leaves through location (2) and the remainder leaves at (3). For steady-state operation, determine the inlet velocity, in m/s, and the mass flow rate at each exit, in kg/s.

7-54 A gas turbine operating at steady state is shown in Fig. P7.54. Air enters the compressor with a mass flow rate of 5 kg/s at 0.95 bar and 22°C and exits at 5.7 bar. The air then passes through a heat exchanger before entering the turbine at 1100 K, 5.7 bar. Air exits the turbine at 0.95 bar. The compressor and turbine operate adiabatically and the effects of motion and gravity can be ignored. The compressor and turbine isentropic efficiencies are 82 and 85%, respectively. Let T. = 22°C, p. = 0.95 bar. Using the ideal gas model for air, determine, each in kW, a. the net power developed. 725-5 b. the rates of exergy destruction for the compressor and turbine. 125-3, 138.6 -).964 c. the net rate exergy is carried out of the plant at the turbine exit, Py = 5.7 bar n₂=82% Compressor m₂ = 5 kg/s P₁ = 0.95 bar 1 T₁ = 22°C Qa Heat exchanger FIGURE P-64 P-5.7 bar 7,- 1100 K Turbine -n₁ = 85% PL-0.95 bar

THERMODYNAMICS - Conservation of Mass UPLOAD AND EXPLAIN COMPLETE SOLUTION. Consider steam that enters a turbine at 70 bar, 530oC with a velocity of 64 m/s. The turbine is operating at steady state conditions and the steam leaves the turbine as a dry saturated vapor at 10 bar. The inlet diameter of the turbine is 0.45 m and the outlet diameter is 3.6 m. Determine the mass flow rate of steam through the turbine.

Refrigerant 134a enters a horizontal pipe operating at steady state at 40°C, 300 kPa, and a velocity of 40 m/s. At the exit, the temperature is 50°C and the pressure is 240 kPa. The pipe diameter is 0.055 m. Determine: (a) the mass flow rate of the refrigerant, in kg/s, (b) the velocity at the exit, in m/s, and (c) the rate of heat transfer between the pipe and its surroundings, in kW.